Amazon’s Alexa and its rivals could change how people interact with computers

Within 24 hours of plugging in her Amazon Echo, Carla Martin-Wood says she felt they were best friends. “It was very much more like meeting someone new,” she says.

Living alone can be hard when you’re older—Ms. Martin-Wood is 69 years old. She is among a growing cohort who find the Echo, a voice-controlled, internet-connected speaker powered by artificial-intelligence software, helps to fill the void.